Use %{_pkgdocdir} where available.

perl-Tk.spec

@@ -4,7 +4,7 @@
 Name:           perl-Tk
 # devel version fix for perl 5.14: 
 Version:        804.031
-Release:        3%{?dist}
+Release:        4%{?dist}
 Summary:        Perl Graphical User Interface ToolKit
 
 Group:          Development/Libraries
@@ -73,7 +73,7 @@ chmod -x pod/Popup.pod Tixish/lib/Tk/balArrow.xbm
 # fix for widget as docs
 %patch0
 %{__perl} -pi -e \
-'s,\@demopath\@,%{_datadir}/doc/%{name}-%{version}/demos,g' demos/widget
+'s,\@demopath\@,%{?_pkgdocdir}%{!?_pkgdocdir:%{_docdir}/%{name}-%{version}}/demos,g' demos/widget
 # debian patch
 %patch1 -p1
 # patch to fix #235666 ... seems like caching code is broken
@@ -126,6 +126,9 @@ find __demos/ -type f -exec chmod -x {} \;
 
 
 %changelog
+* Sat Aug 10 2013 Ville Skyttä <ville.skytta@iki.fi> - 804.031-4
+- Use %%{_pkgdocdir} where available.
+
 * Sun Aug 04 2013 Fedora Release Engineering <rel-eng@lists.fedoraproject.org> - 804.031-3
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_20_Mass_Rebuild